Made possible what's accomplished, in conclusion (7)
I believe the answer is:
enabled
'made possible' is the definition.
(I've seen this before)
'accomplished in conclusion' is the wordplay.
'accomplished' becomes 'able' (I've seen this before).
'in' indicates putting letters inside.
'conclusion' becomes 'end' (end is a kind of conclusion).
'able' put inside 'end' is 'ENABLED'.
'what's' is the link.
(Other definitions for enabled that I've seen before include "Allowed" , "Permitted" , "Made possible, facilitated" , "Made something possible" , "Be laden (anag.)" .)